Aresearcher while working in vitro (outside cell) added helicase enzyme which resulted in the untwisting of the dna helix. but this untwisting led to strain ahead of the replication fork. which enzyme can be added to correct this problem

The enzyme needed is topoisomerase. Topoisomerases are enzymes whose function is to regulate the unwinding of the DNA double helix. They ensure there is no overwinding or underwinding of the helix. During the replication and transcription of DNA, the double helix becomes overwound ahead of the replication fork. If left to go on, the tension created would eventually hinder the ability of DNA and RNA polymerase enzymes to continue down the strand of DNA. Topoimerases I and II enzymes correct this, ensuring the polymerase enzymes do their work smoothly.

The answer is atmosphere. there are four spheres of the earth: 1. geosphere (from greek word 'geo' = ground), 2. hydrosphere (from greek word 'hydro' = water), 3. biosphere (from greek word 'bio' = life), and 4. atmosphere (from greek word 'atmo' = air). a magnetosphere is a region of space around astronomical objects controlled by the magnetic field of that object. through the process of elimination, since lightning is present in the air, it can be found in the atmosphere.